defmodule PhoenixPubSubPostgres do
  use Supervisor

  @moduledoc """
  The Supervisor for the Postgres `Phoenix.PubSub` adapter

  To use Postgres as your PubSub adapter, simply add it to your Endpoint's config:

      config :my_app, MyApp.Endpiont,
        ...
        pubsub: [name: MyApp.PubSub,
                 adapter: PhoenixPubSubPostgres,
                 hostname: "localhost",
                 database: "myapp_db_env",
                 username: "postgres",
                 password: "postgres"]

  ## Options

    * `name` - The required name to register the PubSub processes, ie: `MyApp.PubSub`
    * `host` - The Postgres-server host IP, defaults `"127.0.0.1"`
    * `port` - The Postgres-server port, defaults `6379`
    * `password` - The Postgres-server password, defaults `""`

  """

  @pool_size 5
  @defaults [host: "127.0.0.1", port: 5432]


  def start_link(name, opts) do
    supervisor_name = Module.concat(name, Supervisor)
    Supervisor.start_link(__MODULE__, [name, opts], name: supervisor_name)
  end

  @doc false
  def init([server_name, opts]) do
    opts = Keyword.merge(@defaults, opts)
    opts = Keyword.merge(opts, host: String.to_char_list(opts[:host]))
    if pass = opts[:password] do
      opts = Keyword.put(opts, :pass, String.to_char_list(pass))
    end

    pool_name   = Module.concat(server_name, Pool)
    local_name  = Module.concat(server_name, Local)
    server_opts = Keyword.merge(opts, name: server_name,
                                      local_name: local_name,
                                      pool_name: pool_name)
    pool_opts = [
      name: {:local, pool_name},
      worker_module: PhoenixPubSubPostgres.Connection,
      size: opts[:pool_size] || @pool_size,
      max_overflow: 0
    ]

    children = [
      worker(Phoenix.PubSub.Local, [local_name]),
      :poolboy.child_spec(pool_name, pool_opts, [opts]),
      worker(PhoenixPubSubPostgres.Server, [server_opts]),
    ]
    supervise children, strategy: :one_for_all
  end
end